Sigma 18-50mm F/2.8 EX DC Lens for Nikon Digital SLR Cameras EX lens series denotes excellence of engineering and new technology. Compact and lightweight zoom despite large F2.8 aperture. Excellent correction for various types of aberration provided by one SLD (Special Low Dispersion) glass element and two aspherical lenses. Super Multi Layer (SML) coating reduces flare and ghosting Focal Length - 18-50mm